Mononuclear copper(II) nitrato complexes with methyl-substituted 4-nitropyridine N-oxide. Physicochemical and cytotoxic characteristics

Three new complexes, products of the interaction of Cu(NO3)2 and methyl-substituted 4-nitropyridine N-oxides were synthesized and characterized by elemental analysis, magnetic, spectroscopic (IR, FIR and EPR), thermal and X-ray methods. The complexes (magnetic moments 1.70–1.81 BM at 300 K) of general formula [Cu(H2O)(NO3)2L2], L = 2-methyl-4-nitropyridine N-oxide and [Cu(NO3)2 L′2], where L′ = 2,6-dimethyl- and 2,3,6-trimethyl-4-nitropyridine N-oxide were obtained. The compounds were unstable upon dissolution. The X-ray single crystal structure of Cu(II) complex with 2,6-dimethyl-4-nitropyridine N-oxide was determined and analysed. The compounds and free ligands were tested in vitro on the cytotoxic activity against MCF-7 and SW-707 human cancer cell lines. The complexes with 4-nitropyridine N-oxide (a reference) and 2-methyl-4-nitropyridine N-oxide show a significant anti-proliferative activity against studied cell lines. A reciprocal relationship between the activity and the number of methyl groups was observed. Both ligands and complexes are cytotoxic active but to the different cell lines.